Two position constant speed semi-automatic propeller pitch control



March 2l, 1961 c. cORUM TwO POSITION CONSTANT SPEED SEMI-AUTOMATIC PROPELLER FITCH CONTROL 5 Sheets-Sheet 1 Filed Deo. 17, 1956 E Il FIG.

INVENTOR. CLINTON CORUM M JW March 21, 1961 coRUM Filed Dec. 17, 1956 C. TWO POSITION CONSTANT SPEED SEMI-AUTOMATIC PROPELLER PITCH CONTROL 3 Sheets-Sheet 2 FIG. 6

INVENTOR.

CLINTON CORUM BY @gi/Mawr,

March 21, 1961 c. coRUM 2,975,838

TWO POSITION CONSTANT SPEED SEMI-AUTOMATIC PROPELLER PITCI-I CONTROL Filed Deo. 17, 1956 5 Sheets-Sheet 3 H iI 'In '9 i l IO se l l fmmlnl IN {l} I. H l.. Il 'n wf l1 H 42 FIG. e lin yI 40 O I O 4o 46 mi Il o "mv If "im I||||| 28 l i Il l IO I9 Hf; IIIH INVENTOR. CLINTON CORUM im BY FIG, lo Mm ff/4W@ TWO POSITION CGNSTANT SPEED SEEE-AUT()- MATIC PROPELLER Pl'iCH CNTRL Clinton Comm, 4225 hfianzanita Drive, San Diego, Filed Dec. 17, 1956, Ser. No. 628,382

2 Claims. (Cl. X70-160.16)

This application is a continuation-impart of pending application Serial No. 308,437, tiled September 8, 1952, in the United States Patent Office, said application having now matured into Patent No. 2,774,433, `and relates to improvements in screw propellers and more particularly to attachment to a semi-automatic propeller for converting the same into what may be considered a two position constant speed propeller, and still more specically to improvements in the arrangement and structure of the auxiliary spring means and the means for controlling the same.

The environment of the present invention is the same as in the invention of the parent case and the objects of the invention described herein include the general objects of the parent application and will be recounted below.

The semi-automatic propeller, sold under the trade name Aerornatic, is widely known and used, and the present invention has been initially designed for combination with this propeller which includes synchronizer links operatively connected with the blades ofthe propeller and with a single piston in a small cylinder disposed axially of the hub, and the device hereinafter disclosed as my invention will be mounted on the end of said cylinder and operatively connected with said piston. The said Aeromatic propeller structure is disclosed in U.S. Patent No. 2,359,265. However, it is quite conceivable that my invention may be used in combination with propeller structures other than the one specifically named above.

As presently supplied, the semi-automatic air-controlled Aeromatic propellers make no provision for loss of power and consequent lowered r.p.m. other than by regulation of the counterweights, which has to be done on the ground. One of the primary objects of this invention is, therefore, to provide means for automatically compensating for the loss of power experienced at higher altitudes.

The term two-position has been chosen for use in this disclosure since my device includes electrically operated means, controlled by the pilot, for effecting one setting or position of functional elements in the device to meet requirements for normal cruising of the aircraft, a second setting or position of these same functional elements being obtainable for use during take-o. The device is designed to secure substantially constant speed of rotation at varying altitudes for cruising and a different and higher constant speed of rotation of the propeller for take-olf at varying altitudes, this -representing an equally important object of the present invention.

Another object of this invention is to provide means making it unnecessary to adjust a semi-automatic propeller, while grounded, as is now necessary or at least denitely desirable when the airport visited varies by 2500 feet in altitude with respect to the elevation of the airport at which the original adjustment of the semi-automatic propeller was made. Such adjustment has heretofore been required because semi-automatic propellers are air controlled and the power output of Patented lidar. 2l, 3195i 2 an aircraft engine varies with the altitude at which it is operated. My invention obviates the necessity of such an adjustment because the pilot can control the engine speed by making the proper setting (position) for takeoit, thus assuring suiiciently high engine speed even at airports of higer altitude. Of course, provision is made for releasing this initial setting after the takeoff has been accomplished and suiiicient altitude obtained.

Still another object of this invention is to provide means for maintaining constant propeller speed at two different settings by varying the pitch of the propeller blades in direct proportion with the actual power being developed, the index to the power actually developed being the propeller speed.

Yet another object of this invention is to provide an attachment achieving the results mentioned in the immediately preceding object and capable of being attached to the above mentioned particular semi-automatic propeller `assembly without any significant change in the original structure thereof.

In addition, it is a specific object of this invention to provide auxiliary spring means and means for controlling the same which will not be `adversely affected by centrifugal force during the operation of the propeller.

Another additional object is to provide for greater ease of access to the various parts of thej pitch control apparat-us. Yet another object of this inventionl is to provide means for locking the auxiliary spring seat in an iniinite number of different positions. This feature increases the utility of the invention, since the pitch control lapparatus can be set for optimum operation in the take-off from airtields at various altitudes.

Another object of this invention is to provide a pitch control apparatus wherein a relatively small solenoid is adequate to operate the same, this feature being related closely tothe elimination of adverse eifects of centrifugal force on the apparatus. In this regard, it should also be mentioned that the auxiliary spring itself has been re-located so as to be unaffected by centrifugal force during the operation of the invention.

Yet another object of the present invention is to provide for means to facilitate the adjustment of the presetting of the elements controlling the preloading of the auxiliary spring.

With these objects definitely in view, this invention resides in the novel construction, combination and arrangement of elements and portions as will be hereinafter described in detail in the speciiication, particularly pointed out in the `appended claims, and illustrated in the accompanying drawings, in which:

Figure l is a vertical, central sectional view of the assembled pitch control apparatus;

Figure 2 is lan elevational view, partially broken away, of the auxiliary control rod supporting tube which also functions as a support for a toggle to engage said rod, the View showing one of three such tubes used in the device;

Figure 3 is an elevational view of one of the auxiliary spring control rods;

Figure 4 is a horizontal cross-sectional view taken substantially on the line 4-4 in Figure l;

Figure 5 is a horizontal sectional view taken substantially on the line 5-5 in Figure l;

Figure 6 is a horizontal sectional View taken substantially on the line 6-6 in Figure l, and looking upwardly in the direction ofthe arrows;

Figure 7 is a plan view of the stop ring;

Figure 8 isa plan view of the spring seat;

Figure 9 is a fragmentary front end elevational View, the view including a fragmentary showing of a hub portion and a blade portion of the propeller assembly, as well as the instant pitch control apparatus; and

Figure l is a plan view of substantially the same structure as represented in Figure 9.

Referring now to the drawings in detail, by means of reference numerals, the same reference numerals referring to the same or similar parts and portions throughout the specification and throughout the different views in the drawings, it will irst be noted that this invention is ad-apted to be used, in an environment including a propeller hub structure having a projecting cylinder 12 wherein a plunger or piston-like element 14 is reciprocally mounted. On the piston-like element 14, a pair of synchronizer links 16 are pivotally mounted by means of the piston pin 18. A pair of propeller blades, one of which is indicated at 19, are conventionally provided and the root portion of each of these blades has thereon a propeller blade pitch control dowel, the dowels tting into the bores 21 in the ends of the synchronizer links 16 remote from the piston pin 18. As is well known, these dowels and synchronizer links are used in Aeromatic propellers to assure that both blades of a propeller will change pitch in unison with each other. In the conventional Aerornatic propeller mechanisms, a plate normally closes the end of the cylinder 12. This plate is removed when the instant invention is applied to the propeller and the instant pitch control apparatus `is secured to the hub assembly 10 in place of the said plate, such attachment requiring extremely little modification of the existing propeller, and any such modification being of a strictly technological nature easily accomplished by any skilled mechanic.

Attachment of the instant pitch control apparatus is easily accomplished, such attachment including the connection of an enl-arged end portion 11 of a pitch control rod 24, to the piston like element 14 to move therewith. The pitch control rod 24 slides axially within a guide tube 26 which is integral with and centrally disposed on a base 28. The cylinder 12 is provided with an attachment ange 38 and a suitable number of screws 32 are used to secure the base 28 to the attachment llange 30, as best illustrated in Figure 1.

'A pair of ftyweights 34 are secured as indicated at 35 to what may be considered the free ends of bell cranks 36. The bell cranks are pivoted, as indicated at 37, to pairs of arms 38 which may be formed integral with the base 28 and which extend diametrically thereof. Links 40 are used to secure the other ends of the bell cranks 36 to lugs 42 and these lugs may be formed integral with the hollow cylindrical easing 44 which extends ooaxially of and outside the guide tube 26. The casing 44 has one end thereof mounted for reciprocal sliding movement on a neck portion 46 of the base 28. It will be clear that reciprocal movement of the casing 44 will result from actuation of the y-weights 34.

The casing 44 is provided with an internal bead-like flange 47 which engages a semi-circular groove deiined by adjacent edge portions of the pressure plate 48 and the stop plate 50. A counter balancing spring 52 is cornpressed between the pressure plate 48 and a corresponding portion of the base 28, this counter balancing spring being arranged coaxially of and outside the guide tube 26. The counter balancing spring is pre-loaded to counter balance the fly-weights 34 and this spring operates essentially as its name implies. Near the end of the guide tube remote from the base 28, there is provided an undercut or groove to receive divided lock ring segments 54 which hold the stop plate 50 in place relative to the guide tube 26, and a lock ring plate 56 is secured by screws 58 to hold the segments 54 in place and thus rigidly secure the stop plate to the guide tube 26.

A pressure disc 60 is threaded on the end of the pitch control rod 24 remote from the base 28 and secured by a lock nut 62. As illustrated three pressure pins 64 are threaded into the pressure plate 48 and extend through bores in the stop plate 50 to engage vthe pressure disc 60, thereby transmitting movement of the pres- 4 l sure plate to the said pressure disc, or at least permitting movement of the pressure disc and the parts connected thereto when the pressure plate 48 is moved in one direction. A solenoid 66, energization of which is controlled by the pilot of the aircraft by means of any suitable electrical circuit, need not be large. The binding posts 67 of the solenoid 66 have leads, one of which is indicated at 68, connected thereto and protective, tubular sheaths, one of which is shown at 69, are secured in bores 71 in the stop plate 50 and extend through bores 73 in the pressure plate 48 and Vbores 75 in the base 28. The solenoid is mounted by means of lugs 70 to the upper ends of the tubes 72 which are threaded into the stop plate 50. Control rods 74 are axially slidably mounted in these tubes, the lower ends of these control rods being threaded, as indicated at 76, into lugs in the auxiliary spring seat 78. Movement in one direction of the control rods 74 and spring seat '78 relative to the pressure plate 48 is limited by enlargements 80 on intermediate portions of the control rods 74, the pressure plate being undercut to receive these enlargements. The ends 81 of the control rods 74 have tool-receiving sockets for adjusting the pre-loading of the auxiliary springs. The tubes 72 also function as supports for the toggles 82, each tube having a lug 84 upon which a toggle 82 is pivoted, as best illustrated in Fig. 2. Each toggle has a heel portion 85 which rides on the corresponding con` trol rod 74 to position the armature end 86 of the toggle a correct distance from the adjacent end of the core 88 of the solenoid `66. It will be understood that one side of each tube 72 is cut away to permit the toggles to contact the control rods. Each control rod 74 is flattened as indicated at 90 and each toggle has a chisel edge 92 which grips the attened portion 90 when the armature ends 86 are attracted by the solenoid 66.

The auxiliary spring 79 is disposed coaxally and exteriorly of the counterbalancing spring 52 and is compressed between the pressure plate 48 and the spring seat 78. The spring seat 78 is a counterbored annulus and is best illustrated in Fig. 8. A cap 94 lits over the end of the casing 44 and secured by spring detents 96.

In reviewing the operation, it may be well first to point out that it is an established fact that an aircraft engine loses power proportionately `as the altitude above sea level is increased. The blade pitch of the semi-automatic or Aeromatic propellers is inherently varied to meet changing flight conditions but this variation is based solely upon normal or full power output of the engine. When the engine is producing this normal output the instant invention remains substantially inoperative, since the yweights 34 vare proportioned to require or produce a substantially accurate counterbalancing of the effect of the spring 52, and under ordinary conditions, these flyweights 34 will result in the pulling of the pressure pins 64 away from the pressure disc 60 to allow free and proper functioning of the pitch control means in Aeromatic propeller systems. However, if the engine overspeeds, the y-weights 34 will pull 4the pressure pins 64 farther toward the base 28 and will fallow propeller blade pitch to be increased by the action of the counterweights normally provided on the Aeromatic propeller, thus increasing the load and slowing the engine back to its cruising speed.

On the other hand, when the engine underspeeds, as it always does with increased altitude, lthe counter-balancing spring 52 overcomes the reduced centrifugal force generated in the fly-weights 34 and the pressure pins 64 are pushed in such a direction as to cause the pressure disc 60 -to pull the piston-like element 14 in such a manner as to decrease the pitch on the propeller blades, thus decreasing the load and allowing the engine to ref gain its normal cruising speed. It will be clear from the foregoing that the instant pitch control apparatus automatically varies the load directly as the power varies. As a result, during take-olf at higher elevations, all

available power, represented by an increased higher rpm. of the engine, is obtained. The increased centrifugal force acting upon the fry-weights 34 must be counteracted and this is accomplished by the pilots use of the solenoid 66.

While the engine is idling, before take-o at this higher altitude, the solenoid is energized. The energized solenoid pulls the inner ends of the dogs S2 in such a manner as to cause chisel edges 92 to engage the control rods '74 and to lock the control rods in their forward or operative position, preventing movement of the spring seat 73 and bringing the auxiliary spring 79 into use. Since the spring 52 is still fully effective and the action of the spring 79 is additive thereto when the spring seat 78 is arrested, the total counteracting force is increased, requiring an increased centrifugal force acting upon the fly-weights 34 to overcome the sum of the effects of the springs. This increased force is accompanied, of course, by an increase in the number of revolutions'per minute, and this increased speed of the engine is reflected in the required increased power necessary for take-off at the higher elevation. in other words, the propeller blades will be yadjusted to optimum pitch for take-off at the elevated airiield when the pilot employs the apparatus as aforesaid.

After take-off, to return to cruising rpm., it is only necessary to release the control rods 74 by de-energizing the solenoid 66, accomplished by the pilot in the obvious manner. The engine is then throttled to a considerably lower speed momentarily to allow the dogs 82 to disengage, whereafter the engine will be returned to full speed and the blades will be automatically maintained at the cruising on-speed r.p.m. setting of the apparatus. it may be noted, in this regard, that the dogs 82 may be so arranged -that centrifugal force will ordinarily urge die dogs into such positions that the chisel edges 92 will not be in engagement with the control rods 74, although the heel portions 85' of the dogs may ride upon the iiats 99 of the control rods without affecting their free movement.

All the objects recited above are achieved b-y the apparatus disclosed hereinabove, and particular attention is again directed to the fact that all the control means for the auxiliary spring 79, as well as virtually all other portions of the apparatus, are not deleteriously affected by centrifugal force when the propeller is rota-ted. Other advantages will also now be evident in relation to the infinitely great number of settings possible, the proper setting for take-off at `any altitude being automatically achieved by simply idling the motor before take-off and energizing the solenoid `66. Accessibility to yall parts of the apparatus is also facilitated, and the general eiiciency of the apparatus is increased by the present invention.

While a preferred embodiment of the invention has been described and illustrated herein, I do not wish to be limited to the precise form disclosed, and the above description and accompanying drawings are proposed as illustrative rather than limiting.

I claim:

1. A propeller pitch control mechanism, comprising: a semi-automatic, air-controlled propeller having pitch adjustable blades; a plunger coupled to said blades and mounted to move along the propeller axis of rotation with pitch change of the blades; a iiyweight counterbalancing spring operatively connected with said plunger to bias the plunger in one direction; flyweights operatively connected to said counterbalancing spring so that extension of said iiyweights under inertia overcomes the counterbalancing spring and releases said plunger for movement independently of the flyweights, and whereby said counterbalancing ispring is operatively connected with said plunger when saiid iiyweights have less than a predetermined extension due to reduced inertia, said counterbalancing spring thereby retarding pitch change of said blades; an auxiliary counterbalancing spring operatively connected with said plunger; control rods connected to said auxiliary spring and mounted for movement parallel to the axis of said plunger; locking means engageable with said control rods; said locking means including dogs ipivotally mounted adjacent said control rods and having edge portions movable to one, engaged position to grip and hold said control rods; said dogs having substantially radially extending portions biased by centrifugal force lto hold said edge portions clear of said control rods; and remotely controlled actuating means operable to move said dogs to said engaged position.

2. A propeller pitch control mechanism, comprising: a semi-automatic, air-controlled propeller having pitch adjustable blades; a plunger coupled to said blades and mounted to move `along the propeller axis of rotation with pitch change of the blades; a iiyweight counterbalancing spring operatively connected with said plunger to bias the plunger in one direction; iiyweights operatively connected to said counterbalancing spring so that extension of said flyweights under inertia overcomes the counterbalancing spring and releases said plunger for movement independently of the flyweights, and whereby said counterbalancing spring is operatively connected with said plunger when said iiyweights have less than a predetermined extension due to reduced inertia, said counterbalancing yspring thereby retarding pitch change of said blades; an auxiliary counterbalancing spring operatively connected with said plunger; supporting means fixed relative to said plunger; control rods connected to said auxiliary spring and being slidable in said supporting means parallel to the axis of the plunger; said auxiliary spring being coupled to said counterbalancing spring to move together therewith; locking dogs pivotally mounted on said supporting means and having edge portions movable to one, engaged position to grip and hold said control rods; said dogs having substantially radially extending portions biased by centrifugal force to hold said yedge portions cle-ar of said control rods; and remotely controlled actuating means operable to move said dogs to s-aid engaged position and lock said control rods at the instant axial position thereof.

References Cited in the tile of this patent UNITED STATES PATENTS 2,341,624 Kieser Feb. 15, 1944 2,609,057 Crowhurst Sept. 2, 1952 2,656,174 Crookston Oct. 20, 1953 2,694,459 Biermann Nov. 16, 1954 2,774,433 Corum Dec. 18, 1956 2,843,212 Lambeck July 15, 1958 

